Analysis of related factors for osteoporosis in ankylosing spondylitis / 中华风湿病学杂志

ABSTRACT

Objective To investigate the role of RANKL/RANK/OPG system in bone metabolism of ankylosing spondylitis (AS) by detecting bone mineral density, bone metabolism factors such as osteoprotegerin (OPG), soluble receptor activator of nuclear factors-κB ligand (sRANKL) and the expression of membrane-bound (mb) RANKL in the peripheral blood T lymphocytes. Methods Bone mineral density of AS patients were measured by dual-energy X-ray absorptiometry (DEXA) and serum levels of OPG, sRANKL,tartrate resistant acid phosphatase 5b (TRACP-5b) and bone alkaline phosphatase (BALP) were determined by enzyme-linked immunosorbent assay (ELISA). The percentages of CD4+/RANKL+ and CD8+/RANKL+ in the peripheral blood were detected with flow cytometry. T-test, x2-test were used for statisical analysis. Results ① The incidence of osteopenia and osteoporosis in AS was 47% and 37% respectively. ② Serum RANKL,TRACP-5b levels and RANKL/OPG ratio were higher in AS patients than those in normal controls (P<0.05).But there was no significant difference in OPG and BALP between AS patients and normal controls. ③There were positive linear correlation between serum levels of RANKL and OPG, sRANKL and TRACP-5b, OPG and TRACP-5b in AS (P<0.01). ④ The prevalence of CD4+/RANKL+ cells in the peripheral blood of AS patients was significantly higher than that in the normal controls (P<0.05). Conclusion There is a high incidence of bone loss in AS patients. Increased bone resorbtion is the feature of bone metabolism in AS.RANKL/RANK/OPG system may play an important role. The imbalance of RANKL/RANK/OPG system may be one of the bone loss mechanisms of AS. CD4 + T lymphocyte may play an important role in osteoclasts differentiation and bone resorption in AS by up-regulating the expression of RANKL.